In the previous sections, we were equipped with a systematic method of finding the derivative of a function by direct use of its definition where we were evaluating a limit of a function. However, using the three-step rule as indicated in that section is very lengthy and possesses no simplicity. To better help us find the derivative of a function, here are some theorems to keep in mind. Once again, your teacher will likely ask you to memorize these theorems. Take your time, review and commit to memory!